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While changing all of the fluids on PERRIN Project 15K we decided that we would take advantage of the situation and not only change the differential fluid but also add a little style and functionality to the rear end. Our rear diff cover is made from high strength, heat-treated cast aluminum. We’ve incorporated cooling fins into the design helping to reduce oil temps, in addition to looking good and cooling the oil better we’ve also increased the oil capacity more than 30% over stock. For a little more info click here.

Needed tools and gear:1)New differential gasket (Can be purchased from any local Subaru dealer)2)1/2” drive wrench3)17mm wrench or socket4)14mm socket5)Jack and jack stands

This is a very straight forward installation that can be done on either a commercial vehicle hoist or floor jack.

Step 1) Raise vehicle to desired height allowing you enough room to move freely. For this you will want to use jack stands to support the vehicle while removing and installing the differential cover. NEVER WORK ON A VEHICLE SUPPORTED ONLY BY A JACK.

Step 2) Once the vehicle is raised to the desired height you will want to use the 1/2”: drive wrench to remove the lower “drain plug”. You will also want to remove the upper “fill plug” at this time as well. Place these two plugs aside to be reinstalled later.

Step 3) Time to remove tension from the differential, this will allow you to remove the studs connecting the differential to the cross support. You’ll need to get a floor jack for this next step. Placing the jack under the differential you’ll want to raise the differential roughly .5”.

Step 4) Using a 17mm socket remove the 17mm nuts securing the differential to the cross support. Remove the studs from the differential and the cross support by using the “Jam-Nut” method. (this is where you “jam” 2 17mm nuts together on one stud. Then you can remove the stud by unscrewing the nut closest to the differential). Repeat this process on the remaining stud. If this method doesn’t work you’ll have to use a stud-extracting tool.

Step 5) Once the two studs are removed from the differential and the cross support, its time to lower the differential. If needed you may want to remove or lower the exhaust system allowing yourself more working room. Because our vehicle had a differential skip plate we had to remove the exhaust. You now should see and have access to all 8 14mm bolts securing the differential cover to the differential. Using a 14mm socket remove the bolts. (NOTE: WHILE REMOVING THE DIFF COVER THERE WILL BE ADDITIONAL OIL THAT WILL BEGIN TO COME FROM THE BOTTOM OF THE DIFFERENTIAL). Once the cover is removed you’ll want to wipe out as much excess oil from the differential as possible.

Step 6) Once everything is clean you can place THE NEW DIFFERENTIAL GASKET to the PERRIN differential cover. Using the 8 14mm bolts remove earlier loosely place the cover back into place. Starting at the top two bolts tighten the bolts to 21.7ft-lbs.

Step 7) Raise the differential back into place using the floor jack. Once the differential is in place (you’ll be able to tell because the differential nut holes will line up with the cross support holes). With everything lined up you’ll want to place and tighten the two bolts/nuts removed earlier to 52ft-lbs. Before doing this thread studs into differential cover until they are bottomed out.